Facile Synthesis of BiVO4@ZIF−8 Composite with Heterojunction Structure for Photocatalytic Wastewater Treatment

Water pollution has always been a serious problem across the world; therefore, facile pollutant degradation via light irradiation has been an attractive issue in the field of environmental protection. In this study, a type of Zn-based metal–organic framework (ZIF−8)-wrapped BiVO4 nanorod (BiVO4@ZIF−8) with high efficiency for photocatalytic wastewater treatment was synthesized through a two-step hydrothermal method. The heterojunction structure of BiVO4@ZIF−8 was confirmed by morphology characterization. Due to the introduction of mesoporous ZIF−8, the specific surface area reached up to 304.5 m2/g, which was hundreds of times larger than that of pure BiVO4 nanorods. Furthermore, the band gap of BiVO4@ZIF−8 was narrowed down to 2.35 eV, which enabled its more efficient utilization of visible light. After irradiation under visible light for about 40 min, about 70% of rhodamine B (RhB) was degraded, which was much faster than using pure BiVO4 or other BiVO4-based photocatalysts. The synergistic photocatalysis mechanism of BiVO4@ZIF−8 is also discussed. This study might offer new pathways for effective degradation of wastewater through facile design of novel photocatalysts.

p-CuO/n-ZnO Heterojunction Structure for the Selective Detection of Hydrogen Sulphide and Sulphur Dioxide Gases: A Theoretical Approach

DFT calculations at the B3LYP/LanL2DZ level of theory were utilized to investigate the adsorption of H2S and SO2 gases on the electronic properties of CuO-ZnO heterojunction structures. The results were demonstrated from the standpoint of adsorption energies (Eads), the density of states (DOS), and NBO atomic charges. The obtained values of the adsorption energies indicated the chemisorption of the investigated gases on CuO-ZnO heterojunction. The adsorption of H2S and SO2 gases reduced the HOMO-LUMO gap in the Cu2Zn10O12 cluster by 4.98% and 43.02%, respectively. This reveals that the Cu2Zn10O12 cluster is more sensitive to the H2S gas than the SO2 gas. The Eads values for SO2 and H2S were −2.64 and −1.58 eV, respectively. Therefore, the Cu2Zn10O12 cluster exhibits a higher and faster response-recovery time to H2S than SO2. Accordingly, our results revealed that CuO-ZnO heterojunction structures are promising candidates for H2S- and SO2-sensing applications.

Simple Fabrication of Visible Light-Responsive Bi-BiOBr/BiPO4 Heterostructure with Enhanced Photocatalytic Activity

A Bi-BiOBr/BiPO4 heterojunction structure was successfully synthesized via a two-step solvothermal method with ethylene glycol as a reducer. Little BiPO4 irregular polyhedrons and little metal Bi spherical nanoparticles were uniformly dispersed on the surface of BiOBr nanosheets with intimate contact and formed a heterojunction structure between BiPO4 and BiOBr. It was found that Bi-BiOBr/BiPO4 had a significant improvement in photocatalytic performance for RhB degradation compared to bare BiOBr and BiPO4. The photocatalytic degradation rate constant of 0.2-Bi/BiOBr/BiPO4 was 1.44 h-1, which was 3.8 times and 14.2 times more than that of bare BiOBr and BiPO4, respectively. This is attributed to the formation of a ternary heterojunction, which benefits the separation of photogenerated electron-hole pairs. Furthermore, with the introduction of metal Bi, the SPR effect of metal Bi can effectively improve the absorption ability of Bi-BiOBr/BiPO4 photocatalyst, resulting in enhanced photoactivity. In this work, the mechanism of photocatalytic degradation was studied by using the photochemical technique and the capture experiment of active species, and it was revealed that h+ and ⋅O2- played a major role in the photocatalytic process.

Fabrication and Sterilization Characteristics of Visible Light Photocatalyst of CuO/ZrO2/CB/Coal-Tar-Pitch-SAC

To provide an effective method of green aquaculture, the photocatalysts of CuO/ZrO2/CB/coal-tar-pitch-SAC, which have visible light sterilization capacity, were successfully fabricated by coating ZrO2 and CuO on the surface of CB/coal-tar-pitch-SAC. The structures of synthesized CuO/ZrO2/CB/coal-tar-pitch-SAC were investigated by XRD, XPS and SEM measurements in detail. It was observed that CuO/ZrO2/CB/coal-tar-pitch-SAC materials possess obvious heterojunction structure and excellent visible light sterilization capacity when the prepared weight ratio of CuO, ZrO2 and CB/coal-tar-pitch-SAC is controlled as 0.03:0.3:1. Our studies can provide a beneficial reference for the design of photocatalysts with sterilization capacity in visible light.